1. Field of the Invention
This invention relates to the field of data processing systems. More particularly, this invention relates to data processing systems including registers for holding input operand data words and output data words from an arithmetic logic unit within said data processing apparatus.
2. Description of the Prior Art
It is known to provide data processing systems incorporating registers for holding the data to be manipulated and the result data. The greater the number of data processing registers available then the more data can be stored in registers with fewer reads from or writes to cache and main memory being necessary. The disadvantage of simply providing ever larger numbers of registers is that the circuit size increases resulting in an increase in complexity and cost and the bit space required to specify an individual register increases making the program instructions less dense.
A further consideration is the bit size of each register. Once again, increasing the size of the registers enable them to store and manipulate a larger amount of data but has the disadvantage of increased complexity and cost together with increased power consumption through the need to continuously write and read the full register width even if the data word being manipulated is considerably narrower.